1. Field of the Invention
The present invention generally relates to a lighting device, and more particularly to a light-emitting diode (LED) lighting device with automatic detection and brightness control.
2. Description of Related Art
Due to various advantages of a light-emitting diode (LED) such as small volume, short response time, low power consumption, high reliability and high feasibility of mass production, the LED is replacing conventional lighting devices such as light bulbs or fluorescent lamps.
LEDs may replace conventional lighting devices in most applications, and may further perform functions not available in the conventional lighting devices. For example, a motion, detector may be used in places not being regularly frequented, such as a garage or courtyard, to detect moving object. The light source will be automatically turned on or the brightness be increased whenever the moving object has been detected; otherwise, the light source will be turned off or the brightness be decreased to save power. Such automatic detection and brightness control technique may be applied to not only the conventional lighting devices but also the LEDs. However, a complex and expensive control circuit, such as a microprocessor, is commonly used in the automatic brightness control system.
The brightness of some conventional lighting devices such as incandescent bulbs or energy saving bulbs may be adjusted, while the brightness of other conventional lighting devices such as fluorescent tubes cannot be adjusted. The brightness adjusting schemes of the conventional lighting devices or LEDs are commonly devised on their lamp holders. Accordingly, a special lamp holder need be purchased beforehand to acquire the brightness adjusting function. Moreover, the brightness adjusting system normally uses the complex and expensive control circuit, such as a microprocessor or dimmer.
For the reason that conventional lighting devices or LEDs could not be flexibly used in some applications and are limited due to high cost or expensive price, the conventional lighting devices thus could not be widely accepted by consumers. Accordingly, a need has arisen, to propose a simple but effective automatic control scheme adaptable to LED light source to expand application scope and reduce cost and price.